WO1994013653A1

WO1994013653A1 - Method of preparing 3,4-epoxy-1-butene

Info

Publication number: WO1994013653A1
Application number: PCT/EP1993/003352
Authority: WO
Inventors: Stefan Boeck; Klaus Herzog; Rolf Fischer; Herbert Vogel; Martin Fischer
Original assignee: Basf Aktiengesellschaft
Priority date: 1992-12-11
Filing date: 1993-11-30
Publication date: 1994-06-23
Also published as: DE59305421D1; AU673713B2; AU5629294A; US5618954A; CA2151391A1; KR0184949B1; KR950704285A; EP0677047A1; ATE148696T1; JPH08504413A; ES2098120T3; EP0677047B1; DE4241942A1; US5905161A

Abstract

The invention concerns a method of preparing 3,4-epoxy-1-butene by the gas-phase epoxidation of 1,3-butadiene by oxygen or oxygen -containing gases over silver-containing catalysts, and the isol ation of the 3,4-epoxy-1-butene from the reaction products. This is achieved by carrying out the gas-phase epoxidation in the presence of 6 to 80 mole % of steam, calculated relative to the gas mixture fed to the reactor.

Description

Process for the preparation of 3,4-epoxy-1-butene

description

The present invention relates to a process for the preparation of 3,4-epoxy-1-butene by the gas phase epoxidation of 1,3-butadiene by means of oxygen or oxygen-containing gases over silver-containing catalysts and isolation of the 3,4-epoxy-1-butene from the reaction discharge .

3,4-epoxy-1-butene, also referred to as butadiene monoxide or vinyl oxirane, is an intermediate for the production of, for example, tetrahydrofuran, which, for example, can be prepared by the process of US Pat. No. 5,034,545 by isomerization to 2,5-dihydrofuran and its subsequent hydrogenation. It is also used for the production of 1,2-butylene oxide (cf. US Pat. No. 5,117,013). An efficient, economical process for the production of 3,4-epoxy-1-butene is required for the economical production of the aforementioned chemicals, which are required in large quantities, based on the starting material 3,4-epoxy-1-butene. Such a method is not yet available.

For example, WO 89/07101 describes a process for the gas phase epoxidation of 1,3-butadiene with oxygen or oxygen-containing gases over silver-containing catalysts. The yields and selectivities achieved are initially quite good, but the silver-containing catalysts used decrease their activity very quickly and almost lose within 24 hours

90% of their original activity. This process is therefore unsuitable for the production of 3,4-epoxy-1-butene on an industrial scale.

This deactivation is presumably caused by the coating of the catalyst surface with decomposition products of vinyloxirane, a process which is referred to below as coking. In the following, unless otherwise noted, deactivation is understood to mean the deactivation of the silver catalyst by coking processes in the production of vinyloxirane, which leads to a rapid decrease in activity, ie an activity decrease by more than 50% of the initial activity within a few hours or days silver-containing catalyst leads. This type of deactivation is due to the normal deactivation of the silver-containing catalyst as a result of aging processes that only appear in the course of months and years, such as thermal damage to the catalyst, sintering processes, To distinguish phase segregation or the gradual discharge of catalyst components.

US Pat. No. 5,117,012 relates to a process for working up the gaseous reaction discharge from the gas phase epoxidation of 1,3-butadiene according to the process of WO 89/07101, in which the hot, gaseous reaction discharge is carried out using liquid 1,3-butadiene is deterred. In this document it is mentioned that the reactor feed from 1,3-butadiene, oxygen and inert gas should contain less than 5 mol%, based on the total feed, of water, since otherwise with considerable losses of 3,4-epoxy-1 -butene due to diol formation.

The present invention was based on the object of using a process for the gas phase epoxidation of 1,3-Bu adiene

Finding oxygen or oxygen-containing gases which makes it possible to produce 3,4-epoxy-1-butene on an industrial scale in an economical manner, the activity of the catalysts used in particular being retained over the long term.

Accordingly, a process for producing

3, 4-epoxy-l-butene found by the gas phase epoxidation of 1,3-butadiene using oxygen or oxygen-containing gases on silver-containing catalysts and isolation of the 3,4-epoxy-l-butene from the reaction product, which is characterized in that is that the gas phase epoxidation is carried out in the presence of 6 to 80 mol% of water vapor, based on the gas mixture fed to the reactor.

Furthermore, a process for reactivating catalysts used for the production of 3,4-epoxy-1-butene by the gas phase epoxidation of 1,3-butadiene by means of oxygen or oxygen-containing gases and deactivated by coking, silver-containing catalysts, was found characterized in that the deactivated, silver-containing catalysts are treated at from 100 to 400 ° C. with water vapor and gases containing oxygen or oxygen.

The process according to the invention surprisingly enables long-term operation of the gas-phase epoxidation of 1,3-butadiene with the aid of silver-containing catalysts without any significant loss of activity of the silver-containing catalysts resulting from coking. In addition, the process according to the invention makes it possible to reactivate a large part of its original activity in the gas phase epoxidation of 1,3-butadiene in the case of catalysts which have already been deactivated. The reason for these surprising effects of adding water to the gaseous feed to the epoxidation reactor has not yet been clarified. Surprisingly, even in the case of a large amount of water being added to the gaseous feed to the epoxidation reactor, the high selectivity of the silver-containing catalyst with regard to the production of vinyloxirane is retained.

The water added to the gaseous feed to the epoxidation reactor is generally 6 to 80 mol%, advantageously 8 to 70 mol% and particularly preferably 10 to 50 mol%, based on the total gaseous feed to the reactor. When the water additive is stated in mol%, it is assumed that the gases in the gas mixture behave approximately like ideal gases, so that the m mol% statement practically corresponds to a vol.% Statement. The water is expediently metered in the form of steam to the gaseous feed, the addition of the water by means of atomizers or other devices for introducing water into a gas stream is likewise possible.

To carry out the process according to the invention, a gas strona consisting of 1,3-butadiene, oxygen, the water and, if desired, inert gaseous diluents, such as nitrogen, argon, hydrocarbons, such as methane or, under the reaction conditions used Ethane and / or carbon dioxide and / or reaction moderators, such as nitrogen oxides and / or halogen alkanes with at least one hydrogen atom in the molecule, such as methyl chloride, methyl bromide, dichloromethane, dibromomethane, chloroform, bromoform, ethyl chloride, ethyl bromide, dichloroethane, dibromoethane, Vinyl chloride, dichlorethylene, trichlorethylene, dichloropropane, dibromopropane, dichloropropene, dibromopropen, chlorobutane etc., passed into the reactor. As a rule, a butadiene / oxygen molar ratio of 0.05 to 40, preferably 0.1 to 25 and in particular 0.3 to 15 is set. The volume fraction of butadiene in the feed to the reactor is generally 5 to 80% by volume, preferably 10 to 70% by volume and particularly preferably 15 to 45% by volume, and the volume fraction of oxygen in the feed to the reactor is generally 2 to 80% by volume, preferably 3 to 70% by volume and particularly preferably 5 to 45% by volume.

Preferred inert gases are nitrogen and the C 1 -C -alkanes, particularly preferably the C 1 -C -alkanes, in particular the methane, are used as inert, gaseous diluents. The inert gas in question or a mixture of two or more gases inert under the reaction conditions, preferably two or more of the aforementioned inert gases, particularly preferably the alkanes mentioned and in particular the methane added to the gas feed in such quantities that the gas mixture fed to the reactor contains 2 to 87 vol.%, preferably 5 to 79 vol.% and particularly preferably 10 to 70 vol.% of the inert gas in question. It was found that 5 by adding the hydrocarbons mentioned to the gas feed of the process according to the invention, the oxygen / butadiene molar ratio can be set to higher values than when using the inert gas nitrogen alone, without this mixture being ignitable, ie explosive , becomes. In addition to economic advantages, this effect leads to a considerable gain in safety when operating the method according to the invention.

The reaction moderators, the addition of which serves to inhibit the further oxidation of vinyloxirane to carbon dioxide and water, 15 are generally present in amounts of 0 to

10,000 mol-ppm, preferably from 0.1 to 1000 and in particular from 0.2 to 100 mol-ppm, based on the total gas mixture.

This gas feed is generally at temperatures from 100 ° C. to 400 ° C., preferably from 120 to 350 ° C. and particularly preferably from 150 to 300 ° C. and at a pressure from 0.1 to 100 bar, advantageously from 0 , 5 to 50 bar, in particular from 1 to 30 bar, passed over the silver-containing catalyst and partially oxidized.

25 Under the conditions used, the reaction gases butadiene, water and vinyloxirane are in the gaseous or supercritical, fluid state. In the preferred, continuous mode of operation of the method, the space velocity of the gas inlet is generally 20 to 20,000 h ^-1 , preferably from 50 to

30 15,000 h ^-1 and particularly preferably from 100 to 10,000 h " ¹ .

The conversion of butadiene is generally adjusted to 0.5 to 100 mol%, advantageously to 2 to 80 mol% and particularly preferably to 5 to 20 mol% of the total amount of 1,3-butadiene added. 35 The conversion of butadiene can be controlled via the space velocity of the gas feed, the temperature of the catalyst bed and the addition of the halogen-containing reaction moderators.

The process according to the invention is preferably operated continuously, it being possible advantageously to use tubular or tube-bundle reactors in which the catalyst is advantageously arranged in a fixed bed. These reactors are preferably operated isothermally, it being possible to use customary heat carriers, for example water, hydrocarbons such as kerosene, naphthalene 45 or biphenyl, and molten salts for such purposes. Water is generally preferred as a heat carrier. In the isothermal mode of operation, the silver-containing catalyst can be arranged in the fixed bed both in a loose catalyst bed which is traversed by the heat transfer tubes and in tubes which are thermostatted from the outside. 5

For working up, the hot reaction gas leaving the catalyst bed, the vinyloxirane, unconverted 1,3-butadiene, optionally containing inert gases and / or reaction moderators, is cooled, for example by means of direct heat exchange, e.g. by injecting a cool solvent or by injecting a cool gas such as nitrogen, air, carbon dioxide etc. into the hot reaction gas or preferably by means of indirect heat exchange, e.g. by conventional coolers or heat exchangers, the hot reaction gas 5 advantageously being used for preheating the reactor feed. After the reaction gas has cooled, the vinyloxirane can be used in a suitable manner, e.g. be removed from the gas stream by condensation, or preferably by washing the reaction gas in a gas scrubber with a suitable solvent. For this purpose, the solvent used is advantageously selected from those solvents from which the vinyloxirane and / or 1,3-butadiene can be removed in a simple manner. A suitable solvent of this type is e.g. 1,3-butadiene itself (cf. US Pat. No. 5,117,012), water is particularly preferably used for washing out the vinyl oxirane from the reaction gas. While vinyl oxirane dissolves in water, 1,3-butadiene is practically insoluble in water. In a gas-liquid separator, the water-containing, gaseous 1,3-butadiene and the other water-insoluble constituents of the reaction gas can be separated off from the vinyloxirane-containing, aqueous phase and returned to the reactor. From the aqueous phase the vinyl oxirane can be easily, e.g. by passing through water vapor, air, nitrogen, carbon dioxide and / or other gases which are inert to vinyloxirane under these conditions and, if necessary, after

35 a further purification by distillation can be isolated in pure form.

The temperature of the water for extracting the vinyl oxirane from the reaction discharge is generally up to

40 100 ° C, preferably at temperatures up to 80 ° C, especially at temperatures up to 60 ° C. For the extraction of the vinyl oxirane from the reaction discharge, conventional devices such as those used for the extraction or absorption of gases, e.g. Extraction columns.

45 The carbon dioxide produced as a by-product in the production of vinyloxirane can, if desired, have a washing action from the reaction product freed from vinyloxirane with the aid of suitable solvents or absorbents, in particular a basic agent, such as N-methylpyrrolidone, N-methyldiethanol - Amm, N-methylethanolamm, or aqueous alkali allhydrogen carbonate solutions are extracted. If desired, the carbon dioxide can then be desorbed again from these absorption liquids, for example by heating or stripping with steam or inert gases, and can be used further.

The gas mixture freed from vinyloxirane and carbon dioxide in this way, which essentially consists of 1,3-butadiene, water vapor and inert gases, is advantageously returned to the reactor for the production of vinyloxirane, the content of the recirculated gas hereinafter referred to as circulating gas, 1, 3-butadiene, steam, oxygen, inert gas and reaction moderators is expediently set by metering in these gases to an optimum content for the production of vinyloxirane. To avoid the accumulation of by-products in the cycle gas, it can be advantageous to exclude a small proportion of the cycle gas, generally not more than 15% by volume, from the cycle gas stream.

The catalysts used in the process according to the invention are silver catalysts which contain 0.1 to 50% by weight of silver, advantageously 1 to 30% by weight and particularly preferably 2 to 20% by weight of silver, calculated as Ag and based on the total weight of the catalyst contained on a support material. Pure silver, e.g. Silver crystal powder or electrolyte silver can also be used.

A large number of support materials, such as silicon dioxide, can be used as support materials for such silver-containing catalysts.

35 aluminum oxides, silicon-aluminum mixed oxides, titanium oxides,

Lanthanum oxide, magnesium oxide, boron nitride, boron carbide, silicon nitride, silicon carbide, zinc oxide, tin oxides, iron oxides, calcium oxide, barium oxide, strontium oxide, zirconium dioxide, carbon, boron phosphate, zirconium phosphate, thorium oxide, gallium oxide, indium oxide

40 or similar carrier materials, alone or mixed with other carrier materials.

In general, carrier materials are used which have a BET surface area of less than 50 m ² / g, preferably less than 45 10 m ² / g and in particular less than 2 m ² / g. Particularly preferred carrier materials include the aluminum oxides, in particular the α-aluminum oxide, zirconium dioxide, mixtures of α-alumina and zirconia, titanium dioxide, silicon dioxide and silicon carbide. The porosity of these carrier materials is generally 5 to 90%, preferably 10 to 80%, measured by the method of mercury porosimetry.

The external shape of the catalyst supports is generally not critical for the catalyst activity in the process according to the invention. For example, Carriers in the form of balls, cylinders, rings, saddle bodies, spirals or other shapes are used, preferably rings, balls or saddle bodies are used, which generally have a sufficient geometric surface and only a low pressure loss of the Ka ¬ cause catalyst flow through reaction gas.

Silver catalysts which contain 0.001 to 10% by weight of promoters in addition to the silver and the carrier material are preferably used in the process according to the invention. Suitable promoters are e.g. Alkali metals and alkaline earth metals, the rare earth metals, the metals of the IV., V., VI., VII., VIII. And II. Subgroup of the periodic table of the elements as well

Copper, gold and thallium. Particularly preferred promoters are the alkali metals and alkaline earth metals, in particular the heavy alkali metals potassium, rubidium and cesium, and the elements of VI. and VII. Subgroup of the Periodic Table of the Elements, in particular molybdenum, tungsten and rhenium. The chemical form in which these promoters are present or act in or on the silver-containing catalyst is not yet known.

In general, these promoters are applied to the carrier material in question in the form of their salts, in particular their halides, nitrates, carboxylates, sulfates, carbonates or phosphates, their oxides or hydroxides. The type of anions of the salts of the promoters used is generally of less importance for the catalytic activity of the silver catalysts doped with the promoters. Salts, oxides or hydroxides which are soluble in the solvents used to impregnate the catalyst are preferably used for doping the silver catalysts which can be used in the process according to the invention. Complexes or complex salts of the promoters in question can also be used, for example alkali metal molybdate, alkali metal tungstate or alkali metal rhenate or perrhenate.

An exemplary listing of compounds that can be used as promoters for doping the invention

Catalysts can be used is given below: lithium chloride, lithium bromide, lithium sulfate, lithium nitrate, Lithium carbonate, lithium phosphate, lithium hydroxide, lithium oxide, lithium molybdate, lithium tungsten, lithium rhena, lithium perhenate, lithium aceta, lithium formate, lithium citrate, lithium oxalate etc. and the corresponding salts, hydroxides and oxides of sodium, potassium, rubidium and .Cesium, magnesium nitrate, Magnesium sulfate, magnesium formate, magnesium chloride, magnesium acetate, magnesium citrate etc., calcium chloride, calcium bromide, calcium hydroxide, calcium citrate, calcium acetate, calcium nitrate etc., barium chloride, barium oxide, barium hydroxide, barium nitrate, etc. Particularly preferred are alkali metal salts, alkali metal hydroxides and / or oxides optionally used together with tungsten, molybdenum or rhenium compounds as promoters.

The silver and the promoters can have been applied to the support material in the production of the silver-containing catalysts which can be used in the process according to the invention by the conventional processes for the preparation of catalysts, for example by the silver and the promoters falling onto the support, by drinking the support, by co-precipitating the silver and the other promoters with the carrier material, etc. The order in which the silver and the promoters are deposited on the carrier material can be chosen as desired, in particular in the preparation of the catalysts which can be used according to the invention by impregnating the carrier material , it may be advantageous to drink the silver and the promoters together on the carrier material in one step or to separate the silver and promoters in two steps onto the carrier. The promoter or promoters can be applied to the support before or after the silver. Other variations in the order in which the individual catalyst components are deposited on the carrier are also possible.

Practically all silver compounds can be used to produce the catalysts which can be used in the process according to the invention. Since the silver-containing catalysts are preferably prepared by the impregnation process, silver compounds which dissolve in the impregnation medium, generally water or polar organic solvents, preferably protic organic solvents, are generally preferred as the silver source. Examples of such silver compounds are silver nitrate, silver sulfate, silver acetate, silver oxalate and other silver carboxylates. Soluble complexes of silver, preferably complexes of silver with nitrogen-containing bases, such as ammonia, hydrazine, urea, thiourea, guanidine or organic amines, preferably aliphatic amines, can furthermore advantageously be used to apply the silver. At the boarding of the silver and the respective promoters in one or more stages, the impregnated support can be dried at 20 to 150 ° C., preferably at 50 to 120 ° C., before the support soaked with the silver compound undergoes thermal treatment at temperatures of 150 to 600 ° C, preferably from 180 to 400 ° C for the decomposition of the soaked silver compounds to essentially elemental silver. To further stabilize the silver-containing catalysts prepared in this way, they can, if desired, still be at 200 to

10 800 ° C, preferably calcined at 250 to 600 ° C and / or reduced in the hydrogen flow. The manner in which such catalysts are produced is known per se (cf. WO 89/07101). Suitable silver-containing catalysts which can be used in the process according to the invention are e.g. the catalysts

15 according to WO 89/07101 and US-A 5 081 096.

The addition of water to the gas inlet according to the invention surprisingly enables the process for the production of vinyloxirane by the partial oxidation of 1,3-butadiene with molecular

20 larem oxygen in the gas phase (gas phase epoxidation) to operate long-term without there being any significant loss of activity of the catalyst as a result of coking. With the help of the water additive according to the invention for the gas feed of 1,3-butadiene epoxidation, it is even possible to use silver-containing catalysts which

25 during their use, not according to the invention, as a catalyst for the production of vinyloxirane, having largely lost their catalytic activity as a result of coking within a few hours, to restore most of their catalyst activity, i.e. reactivate them again.

30

However, it is also possible to reactivate by coking deactivated silver-containing catalysts from the production of vinyl oxirane in a separate treatment with gases containing water vapor and oxygen or oxygen. As a rule, this will

35 reactivation carried out in batches, a continuous reactivation of the catalyst by treating it with water vapor and gases containing oxygen or oxygen, e.g. in fluidized bed reactors or rotary kilns, but is also possible. To reactivate the vinyloxirane

40 Production of coked catalyst batches in the reactor, preferably a tubular reactor, water vapor and oxygen or oxygen-containing gases at temperatures of generally 100 to 400 ° C, preferably 150 to 300 ° C and. in particular from 180 to 250 ° C. and a pressure of generally 0.1 to 100 bar, preferably

45 wise from 1 to 30 bar and in particular from 1 to 20 bar. The duration of this catalyst reactivation usually depends on the size of the catalyst batch and the degree of Damage to the catalyst due to coking. The water content of the gas mixture used to reactivate the silver-containing catalysts is generally 5 to 95% by volume, preferably 10 to 80% by volume and particularly preferably 15 to 50% by volume, whereas the oxygen content of the reactivation gas mixture is usually 5 to 95 vol .-%, mainly 10 to 80 vol .-% and in particular 15 to 50 vol .-%. Zweckmäßi¬ gerweise the reactivating gas mixture with a Raumge¬ speed is 20 to 20,000 h ^-1, preferably from 50 to 15,000 h ^_1, and particularly preferably from 100 to 10000 h ^"1 on the deactivated catalyst passed. With the help of erfindungsge¬ According to the catalyst treatment, the deactivated, silver-containing catalysts from the vinyloxirane production can be restored to up to 60% of their original activity.

Examples

In all of the examples, a silver-containing catalyst was used which contained 15.4% by weight of silver, based on the total catalyst, on a support made of α-aluminum oxide, a purity of> 98%. In addition, the catalyst had been doped with 245 ppm by weight of lithium and 550 ppm by weight of cesium, based on the entire catalyst. The α-alumina support had a BET surface area of 0.9 m ² / g (measured according to: Chemie-Ing.-Techn. Vol. 32, 349 (1960); Chemie-Ing.-Techn. Vol. 35, 586 (1963)), a water absorption of 0.47 ml / g (water absorption at 20 ° C. after 5 minutes), a porosity or an average pore diameter, both determined by the method of mercury porosimetry (measuring device: Autopore II, Model 9220 from Micromeritics) of 67% or 10.6 μm and a bulk density of 0.63 kg / 1. 20 ml of the catalyst were placed in the form of grit with a grain size of 2.0 to 2.5 mm in a steel reactor and the reaction gas flowed through at the desired space velocity. The reactor was electrically heated from the outside. The feed gas and the product gas were analyzed by gas chromatography. The conversion U of 1,3-butadiene and the selectivity S of the conversion to butadiene monoxide were calculated from the volume percentages of the individual components in the gas mixture obtained in this way:

1,3-butadiene content in the feed - 1,3-butadiene content in the exhaust gas • 100

U [%] =

1,3-butadiene content in the feed Vinyl oxirane content in the exhaust gas ^• 100 s [%;

1, 3-butadiene content in the inlet - 1,3-butadiene content in the exhaust gas Because of the range of errors in the analysis system, a standard deviation of ± 1 percentage point must be taken into account for the sales value and a standard deviation of ± 2 percentage points for the selectivity value.

The silver-containing catalyst used in the examples was produced by the following procedure:

100 parts by weight of the carrier material made of α-aluminum oxide were soaked in a solution which contains the following constituents: 28.8 parts by weight of silver nitrate, 0.290 parts by weight of lithium nitrate, 0.0723 parts by weight of casium hydroxide, 25.7 Parts by weight of sec-butylamine and 6.3 parts by weight of water. The impregnated support was then converted to the catalyst in a belt calcining furnace under nitrogen at 220 ° C. for 10 minutes and then heated in a chamber furnace to 300 ° C. in air for 5 hours.

Example 1 (not according to the invention)

The catalyst was stirred with a gas mixture of 20 vol .-% of 1,3-butadiene and 20 vol .-% oxygen and the balance nitrogen, at a temperature of 225 ° and at a pressure of 1.5 bar at a space velocity of 1000 ^_1 charged. The results are listed in Table 1.

Example 2

The catalyst from Example 1, deactivated after a running time of 24 h, was mixed with a gas mixture of 20% by volume 1,3-butadiene, 20% by volume oxygen and 8% by volume water vapor, the rest being nitrogen 225 ° C and at a pressure of 1.5 bar with a Raumge¬ speed of 1090 h ^_1 . The test results are shown in Table 1. Table 1

As the comparison of Examples 1 and 2 shows, the deactivation of a catalyst used for the synthesis of vinyloxirane from butadiene and oxygen can be reversed by metering in water vapor.

Example 3 (not according to the invention)

The catalyst was loaded with a gas mixture of 20 vol .-% of 1,3-butadiene and 20 vol .-% oxygen and the balance nitrogen, at a temperature of 220 ° C and at atmospheric pressure with a speed of 250 Raumge¬ h ^_1. The test results are shown in Table 2.

Table 2

Example 4

The catalyst was mixed with a gas mixture of 20 vol.

1,3-butadiene, 20% by volume oxygen and 10% by volume water vapor, the rest nitrogen, at a temperature of 220 ° C. and at atmospheric pressure with a space velocity of 250 h ^-1 . The test results are shown in Table 3. Table 3

As the comparison of Examples 3 and 4 in Tables 2 and 3 shows, the deactivation of a catalyst used for the production of vinyl oxirane from 1,3-butadiene and oxygen can be prevented by metering in water vapor without the selectivity for vinyl oxirane being noteworthy is affected.

Claims

1. Process for the preparation of 3,4-epoxy-1-butene by the gas phase epoxidation of 1,3-butadiene by means of oxygen or oxygen-containing gases over silver-containing catalysts and isolation of the 3,4-epoxy-1-butene from the reaction discharge, characterized in that the gas phase epoxidation is carried out in the presence of 6 to 80 mol% of water vapor, based on the gas mixture fed to the reactor.

2. The method according to claim 1, characterized in that one uses by coking deactivated silver-containing catalysts.

3. The method according to claim 1, characterized in that the 3, 4-epoxy-1-butene is extracted with water from the reaction discharge.

4. The method according to claim 1, characterized in that the 3,4-epoxy-1-butene is extracted with water at a temperature up to 100 ° C from the reaction discharge.

5. The method according to claim 1, characterized in that unreacted 1,3-butadiene from the reaction discharge after Abtren¬ tion of the 3, 4-epoxy-1-butene back into the reactor for the manufacture of 3,4-epoxy l-butene is recycled.

6. The method according to claim 1, characterized in that unreacted 1,3-butadiene from the reaction discharge after separation of the 3,4-epoxy-1-butene and after separation of the carbon dioxide contained in the reaction discharge back into the reactor Production of 3,4-epoxy-1-butene is recycled.

7. The method according to claim 1, characterized in that one carries out the gas phase epoxidation in the presence of 2 to 87% by volume, based on the volume of the gas mixture fed to the reactor, of a Ci to C alkane.

8. The method according to claim 1, characterized in that one carries out the gas phase epoxidation in the presence of 2 to 87 vol .-% methane, based on the volume of the gas mixture fed to the reactor.

9. A process for reactivating 3,4-epoxy-1-butene by the gas phase epoxidation of 1,3-butadiene by means of oxygen or oxygen-containing gases, used by coking deactivated, silver-containing catalysts, characterized in that these catalysts treated at temperatures of 150 to 500 ° C with water and oxygen or gases containing oxygen.